Information on the B&M Limas can be found at:
http://www.steamlocomotive.com/mountain/?page=bm
If you look at the two photos referenced at the end of the page, you'll find the first is clearly using the speed lettering, and the second looks to be numbered in the font (I couldn't read the tender). Also, the 2-book B&M series by Robert Jones has several photos of the Limas, with one in speed lettering on the cover of the 'City and Shore' volume. Given the evidence, and that all the R-1s were named like their P-4 counterparts from the same time period, I think it's safe to say speed lettering is prototypical for the B&M. In fact, although I could find photos of these locos with the square box-lettered tenders, I've seen no photos that could be deemed definitive that the engines themselves were lettered in the same style...
Now getting the engine name plaques along with the speed lettering would be heaven... Even the 3rd-rail release several years ago missed that detail (double checking my 4103).